Endless OS is based on Linux, which offers a high degree of security through a careful and mature design. For this reason and others, Linux tends not to be targetted by authors of malware and viruses.
Endless OS also provides additional degrees of security when compared to other Linux installations:
Viruses designed for Microsoft Windows and most other systems will not run on Endless OS. As a result, you do not need anti-virus software on Endless OS. However, this does not mean that Endless OS is immune to malicious software. You must always remain vigilant and careful regarding any software you install from other sources, and any technical procedures that you are advised to run, which may have malicious intentions in the worst case. You should keep your OS and Apps up to date at all times.